According to the IEEE 802 family of standards Media Access Control (MAC) is the lower sublayer of the OSI data link layer, the interface between a node's Logical Link Control and the network's physical layer. The MAC differs for the various physical media (such as Ethernet, token ring, WLAN).

The MAC sublayer is primarily concerned with

• recognising where frames begin and end in the bit-stream received from the physical layer (when receiving)
• delimiting the frames (when sending), i.e. inserting information (e.g. some extra bits) into or among the frames being sent so that the receiver(s) are able to recognise the beginning and end of the frames
• detection of transmission errors by means of e.g. inserting a checksum into every frame sent and recalculating and comparing them on the receiver side
• inserting the source and destination MAC addresses into every frame transmitted
• filtering out the frames intended for the station by verifying the destination address in the received frames
• the control of access to the physical transmission medium (i.e. which of the stations attached to the wire or frequency range has the right to transmit?)

See also: MAC address, Ethernet, token ring